Route reliability record

IAH→LAS

Houston to Las Vegas

Flights: 3,457
Period: July 2025 to June 2026
Distance: 1,222 mi
Carriers: 3

This route lands a B+, 5 points better than the national rate of 77.6%. About one flight in six arrive 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 3,457 flights, of which United Airlines flew 2,602 at 83.9% on time.

Set against the rest of the country, this route's record is 5 points better than the US average of 77.6%. That gap is worth roughly 48 fewer late arrivals for every thousand flights.

On time

82.4%

Arrivals under 15 minutes late, of 3,427 completed flights

Avg delay

72 min

Across delayed arrivals only, not all flights

Cancelled

0.81%

National rate is 1.81%

Best carrier

United

83.9% on time across 2,602 flights

These figures cover 3,457 flights between July 2025 and June 2026. The median arrival is 10 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.

Carrier by carrier

Which airline is most reliable on IAH to LAS

The two carriers here are closely matched: 2 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.

On-time performance by carrier on IAH to LAS
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	2,602	83.9%	59 min	0.38%	B+
Spirit Airlines	527	81.9%	78 min	2.09%	B
Frontier Airlinesthin sample	328	71.7%	126 min	2.13%	C

No carrier stands out. United tops the table at 83.9%, 2 points clear of the bottom, which is inside the range this kind of sample moves year to year.

Departure window

The best time of day to leave

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 18 points, against 2 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am403 flights93.3%
8am–11am516 flights86.9%
11am–2pm478 flights86.0%
2pm–5pm756 flights82.5%
5pm–8pm583 flights76.9%
8pm–5am721 flights75.1%

Scale runs 65% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 93.3% of the time, against 75.1% for the overnight window. That is 18 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 2pm–5pm window is the busiest, with 756 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 17 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.

Darker means more delays. Figures are on-time percentages.February best, June worst

June is the worst month at 73.9% on time, 17 points below February, the best at 90.9%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. March was the busiest month here, with 323 flights.

Across the week, Wednesday is the strongest day at 89.4% on time and Friday the weakest at 77.0%. 12 points is a smaller lever than departure hour, but it is free.

Delay causes

Why this route gets delayed

Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 43,000 reported delay minutes.

Late-arriving aircraft
37%
Carrier
36%
National Airspace System
22%
Extreme weather
5%
Security
0%

37% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 43,000 reported delay minutes here, that single category outweighs weather by 8 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 43,378 reported delay minutes.

The largest share of delay minutes, 36%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 16,000 of the 43,000 delay minutes reported here.

Cancellations are rare at 0.81%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.

Connections and stage length

What a delay here actually costs

6.4% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route are the a little over an hour kind, which a normal layover absorbs.

The 1,222 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.

The return leg runs 83.9% on time across 3,455 flights, within 2 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.

The sample behind these figures is 3,457 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.

What to do with this

Booking this route

Put together: the calendar is the biggest lever here, not the carrier or the hour. February runs 90.9% on time and June 73.9%, a swing of 17 points. If the dates move at all, move them out of June before you think about anything else. 3,427 completed flights over 12 months sit behind that.

Common questions

IAH to LAS questions

How often is IAH to LAS delayed?

About one flight in six arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 17.6% of the 3,457 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.

Which airline is most reliable on IAH to LAS?

United Airlines leads at 83.9% on time across 2,602 flights. Spirit Airlines is at the other end on 81.9%, a gap of 2 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.

What time of day has the fewest delays on IAH to LAS?

The 5am–8am departure window is the strongest at 93.3% on time. The 8pm–5am window is the weakest at 75.1%, 18 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.

How bad are June delays on IAH to LAS?

June is the weakest month at 73.9% on time, compared with 90.9% in February. Across the year that is 17 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.

Where to go next

Direction matters. IAH to LAS and LAS to IAH are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.

Key figures